WASHINGTON — A criminal evidence recovery team from the Justice Department will be on hand Saturday as BP begins the multi-day task of disconnecting the failed blowout preventer from its Deepwater Horizon oil well in the Gulf of Mexico and lifting it to the surface.

Retired Coast Guard Adm. Thad Allen, the Obama administration's point man on the Gulf oil disaster, said the Justice Department team would be joined in supervising the recovery 48 miles off the Lousiana coast by representatives of a joint Coast Guard-Interior Department commission that is investigating the causes of the April 20 explosion that killed 11 oilrig workers and triggered the gusher that cost the Gulf coast economy billions of dollars in damage.

"They've been allowed unfettered access to observe and record the entire removal process and the recovery process as this takes places," Allen said Friday during a briefing for reporters.

The blowout preventer — a four-story collection of gears and valves that weighs hundreds of thousands of pounds — was the last line of defense for the Deepwater Horizon drilling rig in the event that something went wrong with the well. But its giant rams failed to crush the drill pipe as they were designed to and as a result crude oil and methane surged up the pipe, engulfing the rig in flames for 36 hours before the rig buckled and sank into the sea.

Why the equipment didn't work is a critical question for investigators. BP and the owner of the blowout preventer, Transocean, which BP had hired to drill the well, have blamed one another for the failure.

Allen ordered BP to proceed with the recovery of the blowout preventer even though technicians had failed to remove several pieces of pipe that had become lodged inside it since the Deepwater Horizon's sinking April 22. Allen said technicians had found that the pipes were too fragile to be grasped by equipment lowered into the blowout preventer over the past few days and had concluded that it would be better to leave them in place.

The multi-step process will begin Saturday when technicians disconnect pipes and hoses leading from the blowout preventer to ships on the surface, Allen said. Crews will then remove a containment cap that was placed atop the blowout preventer in July and the blowout preventer itself will then be attached to the Q4000 drilling platform, which will tug it toward the surface, probably on Monday or Tuesday.

That action is likely to provide the only moment of drama of the recovery. Allen said BP still is uncertain whether the blowout preventer is attached to pipe inside the well and that the tugging, which is not exceed 80,000 pounds of force, is intended to see how easily the blowout preventer rises from the seafloor.

If the blowout preventer resists efforts to lift it, its rams will be opened in hopes of detaching any pipe that connects it to the seafloor, Allen said. If it comes up, but is still attached to pipe inside the well, technicians will use robot vehicles to cut the pipe, freeing the blowout preventer to be lifted to the surface, he said.

Allen said government scientists and BP officials thought it was unlikely that any oil would leak from the well during the effort. For all intents and purposes, the well has been dead since Aug. 3, when BP used more than a million pounds of heavy drilling mud to force crude oil in the well back into rock formations 13,000 feet below the seafloor. BP followed that with cement two days later, and Allen and other officials have said a series of tests since have showed that there is no oil leaking into the well.

A relief well intended to ensure that the Deepwater Horizon well is dead won't be completed until after a new blowout preventer is installed. Allen said work would resume on the relief well perhaps as early as Sept. 7 or 8. Crews will attempt to intercept the Deepwater Horizon well about four days after that, Allen said.

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